Method of producing sheets of fibrous material in a stack



Feb. 1, 1966 A. J. A. ASPLUND 3,233,021

METHOD OF PRODUCING SHEETS OF FIBROUS MATERIAL IN A STACK Filed July 12, 1962 I F g 50 4 36 /2 52 45 v v l ARNE JOHAN ARTHUR ASPLUND INVENTOR.

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Mforney United States Patent 3,233,021 METH ZQD 0F PRGDUCTNG SHEETS 0F FIBROUS MATERHAL IN A STACK Arne Johan Arthur Asplund, 11A Grevagen, Bromine, Sweden Filed July 12, 1962, der. No. 209,450 Claims priority, application Sweden, July 14, 1961,

2 Claims. (Cl. 264-109) This invention relates to a method of producing sheets of fibrous material in a stack press.

More particularly this invention relates to a method of producing sheets of fibrous material, preferably organic, such as wood fibers and similar material in a continuously operating press.

Primarily, the invention refers to the manufacture of hard and semihard fiberboard having a thickness of between 6 and 20 millimeters although it is not confined hereto.

A stack press of the type in consideration, usually termed a stack press, has a stack of pressing plates between which sheet blanks are disposed and which are brought upwardly stepwise, in most cases by means of hydraulic lifting means, while the fibrous material is exposed to pressure and heat. At each lifting cycle a pressing plate charged with a wet sheet biank is fed into the lowermost part of the stack, and simultaneously the uppermost plate with a ready pressed sheet thereon is removed. This plate is then charged with a new sheet blank and returns to the stack of plates at the lowermost part of the same.

A continuously operating press is thus understood to be a press having a stack of plates which are charged in turn with blanks of the material to be treated, the plates together with the material then being brought upwardly successively in the press. Hitherto, the heat required for the drying has been supplied while the plates were moving from the lowermost part of the stack toward the top.

One main object of the invention is to bring about an improvement of the drying process in a press of the type in consideration whereby the pressing plates are caused to reach the highest pressing temperature when the sheet blanks begin to be exposed to pressure from the overlying plates of the stack.

A further object of the invention is to bring about an improvement of the drying process in a press of the type set forth wherein the drying of the material is started most intensively immediately when the pressing plate is introduced into the lowermost part of the press, where the pressure has its maximum value. During its travel upwardly through the press the sheet dries and shrinks at the same time as the pressing temperature and pressure decreases successively.

Further objects and advantages of the invention will become apparent from the following description, considered in connection with the accompanying drawing which shows, more or less diagrammatically and in elevation, an embodiment of a plant for carrying into effect the method according to the invention.

Referring to the drawing, reference numeral 10 generally denotes a stack of pressing plates 12 and sheet blanks 14 placed on said plates. Below the press there is disposed a table 16 actuated by a hydraulic lifting device 18. A hydraulically operated pawl device holds fast the lowermost pressing plate when the table 16 descends for the insertion of a new pressing plate with wet fibrous material placed thereon. When the table 16 is then brought back by the hydraulic device 18 to its former position and the pawl device 20 has been made inoperative, the stack of pressing plates and pressing material is brought one step upwards. The uppermost finished sheet 14 is removed at each such raising step of the stack by means of a lifting device 22 operating in accordance with the vacuum principle. Said lifting device is displaceable horizontally on rails 24 assumed to extend perpendicular to the to the plane of the drawing for removal of the sheets. A gripping device 26 carries the uppermost pressing plate 12 along a track 27 to a position 26 above a lowering stand 28, along which the plate is brought down to a rolling table 30 which may be raised and lowered by means of a hydraulic lifting device 32. The pressing plate 12 is moved by a member 34 from the rolling table 3%) into a heating oven 36 having a number of stories each accomodating one pressing plate. The pressing plates 12 are introduced into the stories of the oven 36 in a predetermined order, for instance, in the direction from top to bottom. This is carried out by a programmed adjustment of the level of the table 36. By one pressing plate 12 being fed into the oven, the plate 12 located there is pushed out onto a receiving table 38 having a hydraulic lifting device 40, said last mentioned table thus operating synchronously with the rolling table 30 so as to cause the two tables always to be located straight in front of the same story.

The heating oven 36 is supplied with heat, in the illustrated embodiment by means of a combustion furnace 42 for a combustible substance, such as oil. The combustion gases generated in the furnace 42 pass through a conduit 44 into the oven and are there caused to flow around the pressing plates 12. Through a return conduit 46 and a fan 43 the gases are then conducted back to the furnace 42 for reheating. In the return conduit 46 there may be inserted an outlet 50 controlled by a valve 52 for exhausting some of the combustion gases while fresh air is supplied through a fan aggregate 54. Possibly there may be mounted an air intake 58 in the conduit 44, said intake being controlled by a valve 56 for introducing an adjusted quantity of fresh air, the temperature of the hot combustion gases thus being controlled before entering the heating oven 36.

The pressing plates 12 are heated in the oven 36 to a temperature suitably up to 200350 C., and possibly even higher. Further they have such a heat capacity that they are supplied during the heating with a heat quantity sufficient to carry out the drying process. Each of the plates, being of metal, actually has a weight of several tons.

The table 38 brings the heated pressing plate 12 up to the position indicated by dashed lines where a new Wet sheet blank 14 is put on the plate. They are then pushed by a feeding member 60 onto the table 16 of the stack press, which is then in its lowered position while the overlying pressing plates rest on the pawl device 20, as shown in the figure. When the table 16 is then pushed upwards and the pawl device 20 is relieved, the total weight of the stack of pressing plates above the newly fed in sheet blank will act upon the blank. At the same time the sheet blank is immediately exposed to the highest drying temperature. During operation of the stack press the pressing material moves stepwise upwards, the number of overlying pressing plates being successively reduced at the same time as the temperature of the pressing plates is decreasing. In this manner the pressing procedure will be conducted under very favorable conditions.

A hydraulically operating pawl device 62 may be arranged at the vertically central portion of the stack of plates, and this deviw will then serve to carry the plates on this lever together with the pressing plates thereabove. In this manner it will be possible, during the stepwise lifting of the stack plates, to create momentarily a gap between the locked plate and the underlying sheet blank.

In this Way said freely exposed sheet blank may be aired before it receives it final treatment during the last part of the upward movement. Of course, the pawl device 62 operates stepwise too, so that the full stack pressure acts upon the underlying plates during each operating cycle.

The invention may be combined with embodiments known in prior art according to which additional heat is supplied to the plates when they are in the stack. This extra heat supply may them be effected after the plates have reached a predetermined level in the press.

The additional heating of the pressing plates may also be carried out by means of superheated steam or hot air. Further, the heating plates may be provided with electrical heating elements which thus accompany the plates during the operation. In another embodiment of the invention the heating is brought about by electrical heat ing bodies being introduced into the pressing plates while these are dwelling in the heating oven, after which these bodies are removed when the desired temperature has been reached. As a further alternative, preheated metal bodies may serve as heat accumulators, being introduced into the plates for later removal when the desired temperature has been reached.

While one or more or less specific embodiment of the invention has been shown and described, it is to be understood that this is for purpose or" illustration only, and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.

What I claim is:

1.. In a method of processing wet fibrous material by pressure in a continuously-operating stack press having pressure plates arranged in a stack and carrying interposed sheets of the material being brought upwardly stepwise by lifting means while the material is exposed to heatand pressure and while plates carrying the material to be pressed is fed into the press at, the bottom thereof and the plates with finished sheets thereon are removed at the top of the press, the improvement consisting in sizing said plates to have a relatively high heat storage capacity and successively stacking the plates from which the finished sheets have been removed in a heating means remote from said stack press, heating said plates in said heating means to a temperature at which sutficient' heat is stored to efiiect drying of said sheets without adding additional heat therein in said stack press, successively removing each of the stacked heated plates from the heating means While inserting plates from which the finished sheets have been removed, in place of the removed plates,

then supplying material to the plates as removed from the heating means and feeding said plates with the material borne by them successively back into the press from the bottom thereof, all heat supplied to the plates being that applied thereto in the heating means and remote from the press, there being a constantand continuous reduction in pressure and temperature in the stack press.

2. In a method of. processing fibrous material into sheets by pressure in a continuously-operating stack press having pressure plates arranged in a stack and having interposed sheets of the material brought upwardly andstepwise by lifting means while the material is exposed to heat and pressure and while the plates carrying the material to be pressed are successively fed into the press at the bottom thereof and with the finished sheets being successively removed from the top of the stack, the improvement consisting of sizing said plates to have a relatively high heat storage capacity, heating said plates by heating means situated remote from said stack press to a temperature sufiicient to effect drying of said sheets without adding additional heat thereto in said stack press, said heating means having accommodation for simultaneously heating a plurality of said plates, moving said plates in succession from said heating means in sequence according to the length of time each plate has been in said heating means supplying wet fibrous material to each of said plates as it is removed from said heating means, and transferring said plate, bearing a sheet of the material, to the lower part of said stack, all heat supplied to the plates being that applied thereto in the heating means and remote from the press, therevbeing a constant and continuous reduction in pressure and temperature in the stack press.

References Cited by the Examiner UNITED STATES PATENTS 2,338,697 1/1944 Wacker 264 2,381,269 8/1945 Elmendorf etyal. .a 18-47 2,452,761 11/1948 jesionowski 264 2,619,681 12/1952 Baker et al 13-47 2,873,475 2/1959 Linhorst 18-4 7 2,992,152 7/1961 Chapman 18-47 3,078,506 2/1963 Caughey 18-4 FOREIGN PATENTS 609,431 2/ 1935 Germany. 559,974 3/1944 Great Britain.

ALEXANDER H. BRODMERKEL, Primary Examiner. MORRIS LIEBMAN, ROBERT F. WHITE, Examiners, 

1. IN A METHOD OF PROCESSING WET FIBROUS MATERIAL BY PRESSURE IN A CONTINUOUSLY-OPERATING STACK PRESS HAVING PRESSURE PLATES ARRANGED IN A STACK AND CARRYING INTERPOSED SHEETS OF THE MATERIAL BEING BROUGHT UPWARDLY STEPWISE BY LIFTING MEANS WHILE THE MATERIAL IS EXPOSED TO HEAT AND PRESSURE AND WHILE PLATES CARRYING THE MATERIAL TO BE PRESSED IS FED INTO THE PRESS AT THE BOTTOM THEREOF AND THE PLATES WITH FINISHED SHEETS THEREON ARE REMOVED AT THE TOP OF THE PRESS, THE IMPROVEMENT CONSISTING IN SIZING SAID PLATES TO HAVE A RELATIVELY HIGH HEAT STORAGE CAPACITY AND SUCCESSIVELY STACKING THE PLATES FROM WHICH THE FINISHED SHEETS HAVE BEEN REMOVED IN A HEATING MEANS REMOTE FROM SAID STACK PRESS, HEATING SAID PLATES IN SAID HEATING MEANS TO A TEMPERATURE AT WHICH SUFFICIENT HEAT IS STORED TO EFFECT DRYING OF SAID SHEETS WITHOUT ADDING ADDITIONAL HEAT THEREIN IN SAID STACK PRESS, SUCCESSIVELY REMOVING EACH OF THE STACKED HEATED PLATES FROM THE HEATING MEANS WHILE INSERTING PLATES FROM WHICH THE FINISHED SHEETS HAVE BEEN REMOVED, IN PLACE OF THE REMOVED PLATES, THEN SUPPLYING MATERIAL TO THE PLATES AS REMOVED FROM THE HEATING MEANS AND FEEDING SAID PLATES WITH THE MATERIAL BORNE BY THEM, SUCCESSIVELY BACK INTO THE PRESS FROM THE BOTTOM THEREOF, ALL HEAT SUPPLIED TO THE PLATES BEING THAT APPLIED THERETO IN THE HEATING MEANS AND REMOTE FROM THE PRESS, THERE BEING A CONSTANT AND CONTINUOUS REDUCTION IN PRESSURE AND TEMPERATURE IN THE STACK PRESS. 